Use of water-soluble copolymers comprising N-vinylimidazole units as color transfer inhibitors in detergents

ABSTRACT

The use of water-soluble copolymers which comprise 
     (a) 5-20 mol % of N-vinylimidazole or 4-vinylpyridine N-oxide units, 
     (b) 95-50 mol % of N-vinylpyrrolidone, N-vinyloxazolidone, methyl-N-vinylimidazole units or mixtures thereof and 
     (c) 0-30 mol % of other monoethylenically unsaturated monomer units, 
     and have an average molecular weight M w  of more than 50,000 as color transfer inhibitors in detergents.

The invention relates to the use of water-soluble copolymers based onN-vinylimidazole and N-vinylpyrrolidone as color transfer inhibitors indetergents.

DE-A 2 814 287 discloses detergents which contain 0.1-10% by weight of awater-soluble or -dispersible homo- or copolymer of N-vinylimidazole asdiscoloration-inhibiting additive. The copolymers contain at least 25mol % of N-vinylimidazole units.

EP-A 0 635 565 discloses detergent formulations which contain copolymersof N-vinylimidazole and N-vinylpyrrolidone with an average molecularweight of 5000 to 50,000. The minimum N-vinylimidazole content in thecopolymers is 20 mol %. According to EP-A 0 635 566, the abovementionedcopolymers are used as color transfer inhibitors in detergents whosesurfactant system is free of alkylbenzenesulfonates. The detergents maycontain cellulases or peroxidases as enzyme where appropriate.

The known low molecular weight color transfer inhibitors withvinylimidazole contents above 20% show, in the laundering of coloredtextiles, besides the required effect of color transfer inhibition alsoan upsetting color-releasing effect. In addition, large contents ofanionic surfactants and of polycarboxylates in detergents adverselyaffect the efficacy of the known color transfer inhibitors.

It is an object of the present invention to provide color transferinhibitors for use in detergents, which in the laundering of coloredtextiles have less of a color-releasing effect on the colored textilesthan do known color transfer inhibitors, and whose efficacy is notreduced by anionic surfactants and polycarboxylates to the extent foundwith known color transfer inhibitors.

We have found that this object is achieved by the use of water-solublecopolymers which comprise

(a) 5-20 mol % of N-vinylimidazole or 4-vinylpyridine N-oxide units,

(b) 95-50 mol % of N-vinylpyrrolidone, N-vinyloxazolidone,methyl-N-vinylimidazole units or mixtures thereof and

(c) 0-30 mol % of other monoethylenically unsaturated monomer units,

where the total of (a), (b) and (c) in mol % is always 100, and whichhave an average molecular weight M_(w) of more than 50,000, as colortransfer inhibitors in detergents.

Suitable copolymers are, with the exception of the polymers comprising4-vinylpyridine N-oxide, prepared by copolymerizing the monomers onwhich these copolymers are based. Processes of this type are known, cf.,for example, WO-A 94/26796. Copolymers of 4-vinylpyridine N-oxide can beobtained by copolymerizing 4-vinylpyridine with the group (b) and (c)monomers and subsequently oxidizing the vinylpyridine units tovinylpyridine N-oxide units. Polymers comprising vinylpyridine N-oxideunits are described as color transfer inhibitors in detergents, forexample in WO-A 94/2578.

The content of N-vinylimidazole or 4-vinylpyridine N-oxide units in thecopolymers is 5-20, preferably 5-17.5, mol %. Copolymers comprising8-15% mol % of N-vinylimidazole units are particularly preferred.

The copolymers comprise as component (b) 95-50 mol % ofN-vinylpyrrolidone, N-vinyloxazolidone, methyl-N-vinylimidazole ormixtures of said compounds as copolymerized units. Both2-methyl-N-vinylimidazole and 4-methyl-N-vinylimidazole units ormixtures thereof can be present in the copolymers. The copolymerscomprise 95-50, preferably 62.5-95, mol % of at least one compound ofcomponent (b) as copolymerized units. Copolymers which comprise

(a) 8-15 mol % of N-vinylimidazole units and

(b) 85-92 mol % of N-vinylpyrrolidone units,

where the total of (a) and (b) in mol % is always 100, are particularlypreferred.

The copolymers may comprise where appropriate up to 30 mol % of othermonoethylenically unsaturated monomer units, with the total of (a), (b)and (c) in mol % always being 100.

The group (c) monomers are employed to modify the copolymers ofcomponents (a) and (b). Examples of suitable group (c) monomers arevinyl esters of saturated carboxylic acids, eg. vinyl formate, vinylacetate, vinyl propionate or vinyl butyrate, esters of acrylic acid andmethacrylic acid derived, in each case, from alcohols having 1 to 8carbon atoms, in particular methyl acrylate, ethyl acrylate, isopropylacrylate, n-propyl acrylate, methyl methacrylate and ethyl methacrylate,acrylonitrile, methacrylonitrile, acrylamide and methacrylamide. Estersof other monoethylenically unsaturated carboxylic acids are alsosuitable as group (c) monomers, for example dimethyl maleate.

The average molecular weight M_(w) of the water-soluble copolymers ismore than 50,000, for example 55,000 to 2 million. Copolymers with anaverage molecular weight M_(w) of 75,000 to 500,000 are preferablyemployed according to the invention. The copolymers which are preferablyemployed comprise

(a) 5-17.5 mol % of N-vinylimidazole or 4-vinylpyridine N-oxide units,

(b) 62.5-95 mol % of N-vinylpyrrolidone, N-vinyloxazolidone,methyl-N-vinylimidazole units or mixtures thereof and

(c) 0-20 mol % of other monoethylenically unsaturated monomer units,

where the total of (a), (b) and (c) is always 100. The copolymersdescribed above are present in detergent formulations in amounts of0.05-5.0, preferably 0.1-2.0, % by weight. In the laundering of coloredtextiles they act as color transfer inhibitors in the wash liquor. Theyare employed both in heavy duty detergents and in color detergents. Thecopolymers to be used according to the invention are usually present incolor-sparing color detergents in amounts of 0.1-1.5, preferably0.2-1.0, % by weight.

The detergents comprising the copolymers to be used according to theinvention may be in powder form or else in a liquid formulation. Theycontain the anionic and/or nonionic surfactants which are conventionallyused in amounts of 2-50, preferably 8-30, % by weight. Phosphate-free orreduced phosphate detergents are particularly preferably produced havinga phosphate content not exceeding 25%, calculated as pentasodiumtriphosphate. The detergents may also be in the form of granules or ascompact detergents having a density of 500-950 g/l.

The detergents may be heavy duty detergents or specialty detergents.Suitable surfactants are both anionic and nonionic or mixtures ofanionic and nonionic surfactants. The surfactant content of thedetergents is preferably 8-30% by weight.

Examples of suitable anionic surfactants are fatty alcohol sulfates fromfatty alcohols having 8-22, preferably 10-18, carbon atoms, eg.C₉-C₁₁-alcohol sulfates, C₁₂-C₁₃-alcohol sulfates, cetyl sulfate,myristyl sulfate, palmityl sulfate, stearyl sulfate and tallow fattyalcohol sulfate.

Other suitable anionic surfactants are sulfated, ethoxylatedC₈-C₂₂-alcohols or soluble salts thereof. Compounds of this type areprepared, for example, by initially alkoxylating a C₈-C₂₂-, preferably aC₁₀-₁₈-, alcohol and subsequently sulfating the alkoxylation product.Ethylene oxide is preferably used for the alkoxylation, in which case2-50, preferably 3-20, mol of ethylene oxide are employed per mole offatty alcohol. However, the alcohols can also be alkoxylated withpropylene oxide, alone or with butylene oxide. Also suitable arealkoxylated C₈-C₂₂-alcohols comprising ethylene oxide and propyleneoxide or ethylene oxide and butylene oxide. The alkoxylatedC₈-C₂₂-alcohols may contain the ethylene oxide, propylene oxide andbutylene oxide units in the form of blocks or in random distribution.

Other suitable anionic surfactants are alkylsulfonates such as C₈-C₂₄-,preferably C₁₀-C₁₈-, alkanesulfonates, and soaps such as the salts ofC₈-C₂₄-carboxylic acids.

Other suitable anionic surfactants are linearC₉-C₂₀-alkylbenzene-sulfonates (LAS). The polymers according to theinvention are preferably employed in detergent formulations containingless than 4% of LAS, particularly preferably in LAS-free formulations.

The anionic surfactants are preferably added in the form of salts to thedetergent. Suitable cations in the salts are alkali metal ions such assodium, potassium and lithium ions, and ammonium ions such ashydroxyethylammonium, di(hydroxyethyl)ammonium andtri(hydroxyethyl)ammonium ions.

Examples of suitable nonionic surfactants are alkoxylatedC₈-C₂₂-alcohols. The alkoxylation can be carried out with ethyleneoxide, propylene oxide and/or butylene oxide. It is possible to employas surfactant in this connection all alkoxylated alcohols containing atleast two molecules of one of the abovementioned alkylene oxides in theadduct. Also suitable in this connection are block copolymers ofethylene oxide, propylene oxide and/or butylene oxide, or adducts whichcontain said alkylene oxides in random distribution. 2-5, preferably3-20, mol of at least one alkylene oxide are used per mole of alcohol.Ethylene oxide is preferably employed as alkylene oxide. The alcoholspreferably have 10-18 carbon atoms.

Another class of nonionic surfactants comprises alkyl polyglucosideshaving 8-22, preferably 10-18, carbon atoms in the alkyl chain. Thesecompounds contain 1-20, preferably 1.1-5, glucoside units.

Another class of nonionic surfactants comprises N-alkylglucamides of thegeneral structure II or III

where A is C₆-C₂₂-alkyl, B is H or C₁-C₄-alkyl and C is apolyhydroxyalkyl radical having 5-12 carbon atoms and at least threehydroxyl groups. A is preferably C₁₀-C₁₈-alkyl, B is preferably CH₃ andC is preferably a C₅ or C₆ radical. Compounds of this type are obtained,for example, by acylation of reductively aminated sugars with chloridesof C₁₀-C₁₈-carboxylic acids. The detergent formulations preferablycontain C₁₀-C₁₆-alcohols ethoxylated with 3-12 mol of ethylene oxide,particularly preferably ethoxylated fatty alcohols, as nonionicsurfactants.

The detergents in powder or granule form and, where appropriate,structured liquid detergents additionally contain one or more inorganicbuilders. Suitable inorganic builder substances are all conventionalinorganic builders such as alumosilicates, silicates, carbonates andphosphates.

Examples of suitable inorganic builders are alumosilicates withion-exchanging properties such as zeolites. Various types of zeolitesare suitable, in particular zeolites A, X, B, P, MAP and HS in their Naform or in forms in which Na is partly replaced by other cations such asLi, K, Ca, Mg or ammonium. Suitable zeolites are described, for example,in EP-A 0 038 591, EP-A 0 021 491, EP-A 0 087 035, U.S. Pat. No.4,604,224, GB-A 2 013 259, EP-A 0 522 726, EP-A 0 384 070A and WO-A94/24251.

Examples of other suitable inorganic builders are amorphous orcrystalline silicates such as amorphous disilicates, crystallinedisilicates such as the sheet silicate SKS-6 (manufactured by HoechstAG). The silicates can be employed in the form of their alkali metal,alkaline earth metal or ammonium salts. Na, Li and Mg silicates arepreferably employed.

Other suitable inorganic builder substances are carbonates andbicarbonates. These can be employed in the form of their alkali metal,alkaline earth metal or ammonium salts. Preferably employed are Na, Liand Mg carbonates or bicarbonates, in particular sodium carbonate and/orsodium bicarbonate.

The inorganic builders can be present in the detergents in amounts of5-60% by weight together with the organic cobuilders. The inorganicbuilders can be incorporated either alone or in any combination with oneanother into the detergent. They are added to detergents in powder orgranule form in amounts of 10-60% by weight, preferably of 20-50% byweight. Inorganic builders are employed in structured (multiphase)liquid detergents in amounts of up to 40% by weight, preferably up to20% by weight. They are suspended in the liquid formulation ingredients.

The detergents contain in addition one or more organic cobuilders. Thesecomprise low molecular weight polymeric polycarboxylates.

Examples of suitable polymeric polycarboxylates are

(1) Polymaleic acids obtainable by polymerizing maleic anhydride inaromatic hydrocarbons in the presence of free-radical initiators andsubsequently hydrolyzing the anhydride groups in the polymer, cf., forexample, EP-A 0 451 508 and EP-A 0 396 303. The molecular weight of thepolymaleic acids is preferably 800-5000.

(2) Copolymers of unsaturated C₄-C₈-dicarboxylic acids, suitablecomonomers being

i) Monoethylenically unsaturated C₃-C₈-monocarboxylic acids such asacrylic acid, methacrylic acid, crotonic acid and vinylacetic acid,preferably acrylic acid and methacrylic acid,

ii) C₂-C₂₂-monoolefins, vinyl alkyl ethers with C₁-C₈-alkyl groups,styrene, vinyl esters of C₁-C₈-carboxylic acids, (meth)acrylamide andvinylpyrrolidone, preferably C₂-C₆-α-olefins, vinyl alkyl ethers withC₁-C₄-alkyl groups, vinyl acetate and vinyl propionate, hydroxyalkylacrylates such as hydroxyethyl acrylate, hydroxy-n-propyl acrylate,hydroxybutyl acrylate, hydroxyisobutyl acrylate, hydroxyethylmethacrylate, hydroxypropyl methacrylate or hydroxyisopropyl acrylate,

iii) (meth)acrylic esters of monohydric C₁-C₈-alcohols,(meth)acrylonitrile, (meth)acrylamides of C₁-C₈-amines, N-vinylformamideand N-vinylimidazole.

Examples of suitable unsaturated C₄-C₈-dicarboxylic acids are maleicacid, fumaric acid, itaconic acid and citraconic acid. Maleic acid ispreferred. The copolymers may contain the monomer units of group

i) in amounts of up to 95%,

ii) in amounts of up to 60% and

iii) in amounts of up to 20%.

The copolymers may contain units of 2, 3, 4 or even 5 differentmonomers.

If the group ii) polymers contain vinyl ester units, these can also bepartly or completely hydrolyzed to vinyl alcohol units. Suitable co- andterpolymers are disclosed, for example, in U.S. Pat. No. 3,887,806 andDE-A 4 313 909.

Suitable and preferred copolymers of dicarboxylic acids are

Copolymers of maleic acid and acrylic acid in the ratio 10:90 to 95:5 byweight, particularly preferably those in the ratio 30:70 to 90:10 byweight, with molecular weights of, preferably, up to 10,000. Copolymerswith molecular weights M_(w) of 1000-6000 are particularly preferred.

Terpolymers of maleic acid, acrylic acid and a vinyl ester of aC₁-C₃-carboxylic acid in the ratio 10 (maleic acid):90 (acrylicacid+vinyl ester) to 95 (maleic acid):10 (acrylic acid+vinyl ester) byweight, it being possible for the ratio of acrylic acid to vinyl esterto vary in the range from 20:80 to 80:20 by weight and, particularlypreferably,

Terpolymers of maleic acid, acrylic acid and vinyl formate, vinylacetate or vinyl propionate in the ratio 20 (maleic acid):80 (acrylicacid+vinyl ester) to 90 (maleic acid):10 (acrylic acid+vinyl ester) byweight, it being possible for the ratio of acrylic acid to vinyl esterto vary in the range from 30:70 to 70:30 by weight. The molecularweights M_(w) of the terpolymers are preferably up to 10,000, inparticular 1000-7000.

Copolymers of maleic acid with C₂-C₈-α-olefins in the molar ratio 40:60to 80:20, with copolymers of maleic acid and ethylene, propylene,isobutene or diisobutene in the molar ratio 50:50 being particularlypreferred. The molecular weights M_(w) of these polymers are preferablyin the range from 1000 to 7000.

(3) Graft copolymers of unsaturated carboxylic acids on low molecularweight carbohydrates or hydrogenated carbohydrates, cf. U.S. Pat. No.5,227,446, DE-A 4 415 623 and DE-A 4 313 909.

Examples of suitable unsaturated carboxylic acids are maleic acid,fumaric acid, itaconic acid, citraconic acid, acrylic acid, methacrylicacid, crotonic acid and vinylacetic acid, and mixtures of acrylic acidand maleic acid, which are grafted on, for example, in amounts of 40-95%by weight based on the component to be grafted. It is also possible forup to 30% by weight, based on the component to be grafted, of othermonoethylenically unsaturated monomer units to be present for themodification. Suitable modifying monomers are the above-mentionedmonomers of groups ii) and iii), and acrylamido-2-methylpropanesulfonicacid or sodium vinylsulfonate.

Suitable as grafting base are degraded polysaccharides such asacidically or enzymatically degraded starches, inulins or cellulose,reduced (hydrogenated or reductively aminated) degraded polysaccharidessuch as mannitol, sorbitol, aminosorbitol and glucamine, and sugars, eg.glucose, and polyalkylene glycols with molecular weights of up toM_(w)=5000 such as polyethylene glycols, ethylene oxide/propylene oxideor ethylene oxide/butylene oxide block copolymers, random ethyleneoxide/propylene oxide or ethylene oxide/butylene oxide copolymers,alkoxylated mono- or polyhydric C₁-C₂₂-alcohols, cf. U.S. Pat. No.4,746,456.

Preferably employed from this group are grafted degraded or degradedreduced starches and grafted polyethylene oxides, employing 20-80% byweight of monomers based on the grafting component in the graftcopolymerization. A mixture of maleic acid and acrylic acid in the ratiofrom 90:10 to 10:90 is preferably employed for grafting. The molecularweights M_(w) of the graft copolymers are preferably up to 10,000 and,in particular, 1000-7000.

(4) Polyglyoxylic acid, cf., for example, EP-B 0 001 004, U.S. Pat. No.5,399,286, DE-A 4 106 355 and EP-A 0 656 914. The end groups of thepolyglyoxylic acids may have different structures. The polymerspreferably have molecular weights M_(w) of up to 10,000, in particular1000-7000.

(5) Polyamidocarboxylic acids and modified polyamidocarboxylic acids,cf., for example, EP-A 0 454 126, EP-B 0 511 037, WO-A 94/01486 and EP-A0 581 452.

Preferably used are polyaspartic acid or cocondensates of aspartic acidwith other amino acids, C₄-C₂₅-mono- or dicarboxylic acids, C₄-C₂₅-mono-or diamines. Polyaspartic acids which have been prepared inphosphorus-containing acids and have been modified with C₆-C₂₂-mono- ordicarboxylic acids or with C₆-C₂₂-mono- or diamines are particularlypreferably employed. Particularly preferred modified polyaspartic acidsare those obtainable by condensing aspartic acid with 5-25 mol %, basedon aspartic acid, of tridecylamine or oleylamine and at least 5% byweight, based on aspartic acid, of phosphoric acid or phosphorous acidat from 150 to 230° C., and hydrolyzing and neutralizing thecocondensates. The molecular weights M_(w) of the polycondensates arepreferably up to 10,000 and, in particular, 1000-7000.

(6) Condensates of citric acid with hydroxy carboxylic acids orpolyhydroxy compounds, cf., for example, WO-A 93/22362 and WO-A92/16493. Condensates of this type containing carboxyl groups havemolecular weights M_(w) of up to 10,000, preferably of up to 5000.

The organic cobuilders are present in the detergent formulations inpowder or granule form and in the structured liquid formulations inamounts of 0.5-15% by weight, preferably of 1-8% by weight, togetherwith inorganic builders. Liquid detergent formulations contain organiccobuilders in amounts of 0.5-20% by weight, preferably of 1-10% byweight, particularly preferably of 1.5-7.5% by weight.

The heavy duty detergents in powder or granule form additionallycomprise a bleach system consisting of at least one bleach, possiblycombined with a bleach activator and/or a bleach catalyst.

Suitable bleaches are perborates and percarbonates in the form of theiralkali metal, in particular their Na salts. They are present in theformulations in amounts of 5-30% by weight, preferably 10-25% by weight.Other suitable bleaches are inorganic and organic peracids in the formof their alkali metal or magnesium salts or partly also in the form ofthe free acids. Examples of suitable organic peracids and salts thereofare Mg monoperphthalate, phthalimidopercaproic acid anddiperdodecanedioic acid. An example of an inorganic peracid salt ispotassium peroxomonosulfate (Oxon).

Examples of suitable bleach activators are

acylamines such as tetracetylethylenediamine, tetraacetylglycoluril,N,N′-diacetyl-N,N′-dimethylurea and1,5-diacetyl-2,4-dioxohexahydro-1,3,5-triazine

acylated lactams such as acetylcaprolactam, octanoylcaprolactam andbenzoylcaprolactam

substituted phenol esters of carboxylic acids such as Naacetoxybenzenesulfonate, Na octanoyloxybenzenesulfonate and Nanonanoyloxybenzenesulfonate

acylated sugars such as pentaacetylglucose

anthranil derivatives such as 2-methylanthranil and 2-phenylanthranil

enol esters such as isopropenyl acetate

oxime esters such as acetone O-acetyloxime

carboxylic anhydrides such as phthalic anhydride or acetic anhydride.

Tetraacetylethylenediamine and Na nonanoyloxybenzenesulfonates arepreferably employed as bleach activators. The bleach activators areadded to heavy duty detergents in amounts of 0.1-15% by weight,preferably of 1.0-8.0% by weight, particularly preferably of 1.5-6.0% byweight.

Suitable bleach catalysts are quaternized imines and sulfone imines asdescribd in U.S. Pat. No. 5,360,568, U.S. Pat. No. 5,360,569 and EP-A 0453 003, and Mn complexes, cf., for example, WO-A 94/21777. If bleachcatalysts are employed in the detergent formulations, they are presenttherein in amounts of up to 1.5% by weight, preferably up to 0.5% byweight, and in the case of the very active manganese complexes inamounts of up to 0.1% by weight.

The detergents preferably contain an enzyme system. This comprises theproteases, lipases, amylases and cellulases conventionally employed indetergents. The enzyme system may be restricted to a single enzyme orcomprise a combination of different enzymes. Commercial enzymes are, asa rule, added to the detergents in amounts of 0.1-1.5% by weight,preferably 0.2-1.0% by weight, of the formulated enzyme. Examples ofsuitable proteases are Savinase and Esperase (manufactured by NovoNordisk). An example of a suitable lipase is Lipolase (manufactured byNovo Nordisk). An example of a suitable cellulose is Celluzym(manufactured by Novo Nordisk).

The detergents additionally preferably contain soil-release polymersand/or antiredeposition agents. These comprise, for example,

Polyesters from polyethylene oxides with ethylene glycol and/orpropylene glycol and aromatic dicarboxylic acids or aromatic andaliphatic dicarboxylic acids. Polyesters from polyethylene oxides, whichare end group-capped at one end, with dihydric and/or polyhydricalcohols and dicarboxylic acids. Polyesters of these types are known,cf., for example, U.S. Pat. No. 3,557,039, GB-A 1 154 730, EP-A 0 185427, EP-A 0 241 984, EP-A 0 241 985, EP-A 0 272 033 and U.S. Pat. No.5,142,020.

Other suitable soil-release polymers are amphiphilic graft or othercopolymers of vinyl and/or acrylic esters on polyalkylene oxides, cf.U.S. Pat. No. 4,746,456, U.S. Pat. No. 4,846,995, DE-A 3 711 299, U.S.Pat. No. 4,904,408, U.S. Pat. No. 4,846,994 and U.S. Pat. No. 4,849,126or modified celluloses such as methylcellulose, hydroxypropylcelluloseor carboxymethylcellulose.

Antiredeposition agents and soil-release polymers are present in thedetergent formulations in amounts of 0-2.5% by weight, preferably0.2-1.5% by weight, particularly preferably 0.3-1.2% by weight.Soil-release polymers which are preferably employed are the graftcopolymers of vinyl acetate on polyethylene oxide of molecular weight2500-8000 in the ratio 1.2:1 to 3.0:1 by weight, which are disclosed inU.S. Pat. No. 4,746,456, and commercial polyethyleneterephthalate/polyoxyethylene terephthalates of molecular weight3000-25,000 from polyethylene oxides of molecular weight 750-5000 withterephthalic acid and ethylene oxide and a molar ratio of polyethyleneterephthalate to polyoxyethylene terephthalate of 8:1 to 1:1, and theblock polycondensates which are disclosed in DE-A 4 403 866 and whichcontain blocks of (a) ester units from polyalkylene glycols with amolecular weight of 500-7500 and aliphatic dicarboxylic acids and/ormonohydroxymonocarboxylic acids and (b) ester units from aromaticdicarboxylic acids and polyhydric alcohols. These amphiphilic blockcopolymers have molecular weights of 1500-25,000.

The copolymers to be used according to the invention as color transferinhibitors in detergents are preferably employed in detergents whosesurfactant system is free of alkylbenzenesulfonates. In contrast to thecopolymers of N-vinylimidazole and N-vinylpyrrolidone which aredisclosed in EP-A 635 565 and have a content of N-vinylimidazole unitsof at least 20%, the effect of enzymes, especially proteases andcellulases, in detergents which contain the copolymers to be usedaccording to the invention is surprisingly improved. The copolymers tobe used according to the invention are therefore advantageously employedin detergents which contain enzymes. The copolymers to be used accordingto the invention surprisingly have, despite the low contents ofvinylimidazole or 4-vinylpyridine N-oxide units, a very good colortransfer inhibiting effect which distinctly exceeds that of homopolymersof vinylpyrrolidone or vinyloxazolidone. It was furthermore notpredictable that high contents of anionic surfactants andpolycarboxylates in detergents do not impair the efficacy of thecopolymers to be used according to the invention, or do not impair it asgreatly, as the efficacy of the known copolymers of vinylimidazole andvinylpyrrolidone. Another surprising advantage of the copolymers to beused according to the invention is that they have less of acolor-releasing effect than do the known copolymers of N-vinylimidazoleand N-vinylpyrrolidone with a higher content of N-vinylimidazole, inparticular those with molecular weights below 50,000.

The molecular weights M_(w) were determined by light scattering. Thepercentage data in the examples mean % by weight unless otherwiseevident from the context.

Preparation of the Polymers

Polymer 1

360 g of N-vinylpyrrolidone (VP) and 40 g of N-vinylimidazole (VI) aredissolved in 930 g of water. Nitrogen is passed through this mixture inorder substantially to free it of oxygen, and it is heated to 85° C.under a nitrogen atmosphere. To this mixture is added over the course of2 hours a solution of 8 g of 2,2′-azobis(2-methylbutyronitrile) in 50 mlof i-propanol. In parallel over the same period a 4% by weight aqueoussolution of 2-mercaptoethanol is added dropwise. The mixture is thenstirred at 85° C. for 1 hour. After this, the temperature is reduced to60° C. and, at the same time, 4 g of a 70% by weight aqueous solution oft-butyl hydroperoxide and a solution of 2.8 g of sodium bisulfite in 50g of water are added. The mixture is then stirred at 60° C. for afurther hour. It is finally deodorized by steam distillation. Freezedrying results in 395.7 g of a colorless powder. The average molecularweight Mw of the copolymer is 84,000.

Polymer 2

340 g of N-vinylpyrrolidone and 60 g of N-vinylimidazole are dissolvedin 930 g of water. Nitrogen is passed through this mixture in ordersubstantially to free it of oxygen, and it is heated to 85° C. under anitrogen atmosphere. To this mixture is added over the course of 2 hoursa solution of 2 g of 2,2′-azobis(2-methylbutyronitrile) in 50 ml ofi-propanol. The mixture is then stirred at 85° C. for 1 hour. Afterthis, the temperature is reduced to 60° C. and, at the same time, 4 g ofa 70% by weight aqueous solution of t-butyl hydroperoxide and a solutionof 2.8 g of sodium bisulfite in 50 g of water are added. The mixture isthen stirred at 60° C. for a further hour. It is finally deodorized bysteam distillation. Freeze drying results in 392.5 g of a colorlesspowder. The average molecular weight M_(w) of the copolymer is 900,000.

Polymer 3

3600 g of water and 30 g of vinylpyrrolidone were introduced into aflask with a capacity of 4 l which was equipped with a stirrer, refluxcondenser and thermometer. Nitrogen is passed through this mixture toremove oxygen. It is heated to 73° C. and, over the course of 3 hours,two separate feeds are added to the stirred reaction mixture.

Feed 1 consists of 24 g of N-vinylimidazole (VI) and 486 gN-vinylpyrrolidone (VP). Feed 2 is a solution of 2 g of2,2′-azobis(2-amidinopropane) dihydrochloride in 25 g of water. Afterthe additions are complete, polymerization is continued for 2 hours.

Finally, steam distillation is carried out. Freeze drying results in 539g of a colorless powder. The average molecular weight M_(w) of thecopolymer is 1.5 million.

Polymer 4 (prior art comparison)

Copolymer of N-vinylimidazole and N-vinylpyrrolidone (ratio 1:1 byweight) of molecular weight 15,000

150 g of water are added to a mixture of 30 g of vinylimidazole and 30 gof vinylpyrrolidone monomers. Under a nitrogen atmosphere, the mixtureis heated to 85° C. with stirring. Then, at the same time, a 5% byweight solution of 1 g of 2,2′-azobis(2-methylbutyronitrile) ini-propanol, and 2.2 g of 2-mercaptoethanol dissolved in 50 g of waterare added dropwise. After the addition is complete, the mixture isstirred at 85° C. for 2 hours.

The temperature is then reduced to 60° C. and, at the same time, 0.6 gof a 70% by weight aqueous solution of t-butyl hydroperoxide and asolution of 0.4 g of sodium bisulfite in 8 g of water are added. Themixture is then stirred at 60° C. for a further hour. It is finallydeodorized by steam distillation. Freeze drying results in 58.6 g of acolorless powder.

Polymer 5 (prior art comparison)

Polyvinylpyrrolidone homopolymer of molecular weight 40,000.

The copolymers to be used according to the invention are employed asadditive to the heavy duty detergents indicated in Table 1.

TABLE 1 I II III IV V VI VII Polymer 1 1.5 1.0 0.5 Polymer 2 1.0 0.6Polymer 3 1.0 1.0 AA/MA (70,000) 7.5 5.0 5.0 AA/MA/VAc terpolymer 5.0(40,000) Oligomaleic acid 5.0 Polyaspartic acid 7.5 5.0 Na perboratemonohydrate 15 15 15 7.5 Na percarbonate 18 15 18 TAED 3.8 5.0 4.2 2.0NOBS 4.0 5.0 2.9 Na lauryl sulfate 6.0 12.0 6.0 Na linearalkylbenzenesulfonate 3.1 1.7 0.8 6.5 Sulfated fatty alcohol 5.5ethoxylate Soap 2.8 0.6 0.4 2.5 1.5 2.4 C₁₃/C₁₅ oxo alcohol*3 EO 3.0C₁₃/C₁₅ oxo alcohol*7 EO 4.7 4.7 13.5 4.0 6.5 C₁₃/C₁₅ oxo alcohol*10 EO3.0 C₁₂/C₁₄ fatty alcohol*7 EO 10.0 Lauryl alcohol*13 EO 5.0 Zeolite A25 25 15 30 15 35 Zeolite P 40 SKS-6 14 15 Na disilicate 2.5 3.9 0.5 4.51.5 Mg silicate 1.0 0.8 1.0 1.0 0.6 Sodium sulfate 20 2.5 3.2 2.0 1.55.5 3.4 Sodium bicarbonate 9.0 6.5 Sodium carbonate 12.0 13.6 10.0 8.09.8 Sokalan ® HP 22 0.4 0.5 Polyethylene terephthalate/oxy- 1.0 0.5 0.81.0 ethylene terephthalate Carboxymethylcellulose 0.6 1.3 0.6 1.0 0.60.6 0.5 Dequest ® 2046 (Phosphonate) 0.5 Citric acid 6.8 5.0 2.5 3.8Lipase 1.0 Protease 1.0 1.0 0.5 0.6 Cellulase 0.6 Water to to to to toto to 100 100 100 100 100 100 100 Abbreviations: TAEDTetraacetylethylenediamine NOBS Na nonanoyloxybenzenesulfonate SKS-6Sheet silicate Na salt (manufactured by Hoechst) EO Ethylene oxide AA/MA(70,000) = Acrylic acid/maleic acid copolymer in the ratio 70:30 byweight, molecular weight M_(w) = 70,000 AA/MA/VAc (40,000) = Acrylicacid/maleic acid/vinyl acetate terpolymer in the molar ratio 40:10:50with molecular weight M_(w) = 40,000 Sokalan ® HP 22 Commercial graftcopolymer of vinyl acetate on polyethylene glycol (soil-release polymer)

Table 2 indicates the compositions of color detergents containing thecopolymers to be used according to the invention.

TABLE 2 VII VIII IX X XI XII Polymer 1 1.0 1.0 0.5 1.0 0.5 0.5 AA/MA(70,000) 6.0 5.0 3.5 8.5 Oligomaleic acid 4.5 7.5 Na lauryl sulfate 8.612.5 15.5 Na linear 1.7 7.5 alkylbenzenesulfonate Sulfated fatty alcohol7.5 ethoxylate Soap 2.8 3.0 1.5 1.5 C₁₃/C₁₅ oxo alcohol*3 EO 1.5 C₁₃/C₁₅oxo alcohol*7 EO 6.7 6.0 13.5 4.0 7.5 C₁₃/C₁₅ oxo alcohol*10 EO 6.3Lauryl alcohol*13 EO 2.0 5.0 Zeolite A 28 55 35 37 18 Zeolite P 36 SKS-612 Na disilicate 4.5 0.5 4.5 Mg silicate 1.0 1.0 1.0 1.0 Sodium sulfate24 5.8 11.5 2.0 4.5 7.5 Sodium bicarbonate 6.5 6.5 Sodium carbonate 12.06.0 10.0 9.0 Carboxymethylcellulose 0.6 0.5 0.6 1.0 0.6 0.6 Sokalan ® HP22 1.0 0.5 Polyethylene terephthalate/ 1.0 0.5 0.5 oxyethyleneterephthalate Sodium citrate 2.0 9.0 2.5 Protease 0.5 1.0 1.0 Cellulase1.0 1.0 0.8 1.0 Water to to to to to to 100 100 100 100 100 100 Forabbreviations, see key to Table 1

Use tests

To test the color transfer inhibiting effect, polymers 1-3 were testedas color transfer inhibitors in detergent VIII, comparing with a priorart VI/VP copolymer. The washing conditions are indicated in Table 3,and the results are indicated in Table 4.

White cotton test fabric was washed under the conditions specified inTable 3 with addition of detergent VIII shown in Table 2 in the presenceof dye. The dye was added as dilute solution to the wash liquor readyfor use.

TABLE 3 Washing conditions (color transfer inhibition) MachineLaunder-O-meter Cycles 1 Duration 30 min Temperature 60° C. Waterhardness 3 mmol/l Dye introduced 2.5 g of dyed fabric Test fabric 2.5 gof cotton cheesecloth (bleached) Amount of liquor 250 ml Liquor ratio1:50 Detergent No. VIII from Tab. 2 Detergent concentration 5.0 g/l

The coloring of the test fabric was measured by photometry. Thereflectance measurements on the individual test fabrics were used todetermine the strengths of each of the colorings by the method describedin A. Kud, Seifen, {umlaut over (O)}le, Fette, Wachse 119 (1993)590-594.

TABLE 4 Color transfer inhibition (numbers are color strength units)Deter- Color Direct Direct Direct Direct gent transfer Direct orangeblack red blue No. inhibitor black 22 39 51 212 71 Example No. 1 VIIIPolymer 1 11.7 45.9 65.4 8.7 6.3 2 VIII Polymer 2 10.9 42.2 65.3 8.2 6.53 VIII Polymer 3 11.2 44.1 62.4 7.2 6.4 Comparative example No. 1 VIIINone 188 173 156 110 145 2 VIII Polymer 4 10.5 48.2 64.8 7.3 6.5 3 VIIIPolymer 5 22.5 76.6 91.7 16.0 8.3

The results with the polymers to be used according to the invention showthat the color transfer inhibiting effect of the color transferinhibitors to be used according to the invention is excellent.

The effect of these polymers is distinctly greater than that of purepolyvinylpyrrolidone (polymer 5, Comparative Example 3) and iscomparable with the effect of copolymers with high vinylimidazolecontents (polymer 4, Comparative Example 2).

We claim:
 1. A detergent, comprising at least one surfactant; and awater-soluble copolymer as color transfer inhibitor, wherein thecopolymer comprises: (a) 5-16 mol % of N-vinylimidazole or4-vinylpyridine N-oxide units, (b) 95-50 mol % ofmethyl-N-vinylimidazole units, and (c) 0-30 mol % of othermonoethylenically unsaturated monomer units derived from a vinyl esterof a saturated carboxylic acid, an ester of acrylic acid and methacrylicacid derived, in each case, from an alcohol having 1 to 8 carbon atoms,acrylonitrile, methacrylonitrile, acrylamide or methacrylamide, whereinthe total of (a), (b) and (c) in mol % is 100, and the copolymer hasaverage molecular weight M_(w) of more than 50,000.
 2. A detergent asclaimed in claim 1, wherein the copolymer has an average molecularweight M_(w) of from 55,000 to 2 million.
 3. A detergent as claimed inclaim 1, wherein the copolymer has an average molecular weight M_(w) of75,000 to 500,000.
 4. The detergent as claimed in claim 1, wherein thecopolymer comprises: (a) 5-15 mol % of N-vinylimidazole units, (b)62.5-95 mol % of methyl-N-vinylimidazole units, and (c) 0-20 mol % ofother monoethylenically unsaturated monomer units derived from a vinylester of a saturated carboxylic acid, an ester of acrylic acid andmethacrylic acid derived, in each case, from an alcohol having 1 to 8carbon atoms, acrylonitrile, methacrylonitrile, acrylamide ormethacrylamide, wherein the total of (a), (b) and (c) is
 100. 5. Adetergent as claimed in claim 1, wherein the surfactant system of thedetergent is free of alkylbenzenesulfonates.
 6. A detergent as claimedin claim 1, further comprising enzymes.
 7. The detergent as claimed inclaim 1, wherein said methyl-N-vinylimidazole units are selected fromthe group consisting of 2-methyl-N-vinylimidazole and4-methyl-N-vinylimidazole.
 8. A detergent, based on surfactants, whichfurther comprises, as color transfer inhibitors a water-solublecopolymer, wherein said copolymer comprises: (a) 5-15 mol %N-vinylimidazole or 4-vinylpyridine N-oxide units; (b) 95-62.5 mol % ofa mixture consisting of N-vinylpyrrolidone and methyl-N-vinylimidazole;and (c) 0-30 mol % of other monoethylenically unsaturated monomer unitsderived from vinyl esters of saturated carobxylic acids, esters ofacrylic acid and methacrylic acid derived, in each case, from alcoholshaving 1 to 8 carbon atoms, acrylonitrile, methacvylonitrile, acrylamideor methacrylamide, wherein the total of (a), (b) and (c) in mol % isalways 100, and the copolymer has weight average molecular weight Mw ofmore than 50,000.